2nd display not working properly on bootcamp to windows.

Im running windows 7 on boot camp but never been able to get my second display to work.

it shows the windows start up on both screens when loading up but as soon as get to log in the second display blacks out.

The second display is shown on control pannel, is identified and even knows the resolution but no image appears.

I used automatic updates to check my drivers are up to date.

do i need some sort of third party driver to keep it on once loged in?

Its running out my thunderbolt via a mini-display to VGA.

the second monitor works perfectly well on the Mac side